1、it作形式主语观察例句1It is difficult for a foreigner to learn Chinese.2Its kind of you to help me.3It is no use talking to him about it.4It is a mystery to me how it all happened.5It is believed that the flood there is the biggest in 100 years.归纳用法it作形式主语时没有具体的意义，只是帮助把真正的主语移到句子后面去，使句子显得平衡。it作形式主语时，真正的主语通常是不定
2、式短语、ing短语或主语从句。一、不定式短语作真正的主语，常用于下列句型中：It be 形容词 (for/of sb.) to do sth.It be 名词 to do sth.It takes sb.some time to do sth.干花了某人时间Its up to sb.to do sth.干是某人的职责或义务It is everyones duty to obey the law.遵守法律是每个人的义务。It took them a year to build the bridge.建这座桥花了他们一年的时间。It is bad manners to stare at peopl
3、e.盯着人看是不礼貌的。It is up to us to help those in need.帮助那些有困难的人是我们的责任。名师点津在“Itbe形容词for/of sb.to do sth.”句型中，如果形容词描述的是sb.，则应用介词of；如果描述的是to do sth.就用for。Its necessary for us to use a shortwave radio to pick up the programmes.我们用一台短波收音机收听这些节目是必要的。Its important for us to learn English well.学好英语对我们来说是重要的。It w
4、as foolish of him to give up the job.( He was foolish to give up the job.)他放弃那工作是愚蠢的即学即练1用所给词的适当形式填空It is not up to you to tell(tell) me how to do my job.It is not right to use(use) these places as rubbish dumps.It was nice of them to invite(invite) us.二、ing短语作真正主语的情况远不及不定式短语那么普遍，常限于no good, no use,
5、 useless, waste等词的后面。It is no good/ use having a car if you cant drive.有车如果不会开是没有用处的。It is a waste of time watching TV.看电视是浪费时间的。 It is no use asking him.问他没有用。即学即练2用所给词的适当形式填空Its no good taking(take) over the experience of foreign countries uncritically.Its no use crying(cry) over spilt milk.It is
6、worth making(make) an appointment before you go.三、用it作形式主语，主语从句作真正主语的常见句型有：1It is a pity/ a shame/ a fact/ an honour/ good news/ no wonder/ a wonder. that.It was a pity that the engineer couldnt come.可惜工程师没能来。It is a wonder that he continues to gamble when he always loses!令人惊讶的是他一直输还一直赌。(It is)no wo
7、nder (that) you were late!难怪你来晚了！It is a shame that the rain spoiled our picnic.真可惜，这场雨把我们的野餐给搅了。It is a fact that English is being accepted as international language.英语被认为是国际语言，这是一个事实。2It is 形容词(如： strange/ natural/ surprising/ obvious/ true/ fortunate/ wonderful/ funny/ possible/ impossible/ likel
8、y/ unlikely/ clear/ unusual/ certain/ important.)that.It is certain that he will win.他一定会取胜。It is important that we should learn from each other and help each other.我们应当互相学习，互相帮助，这是很重要的。It was obvious that the child had been badly treated.很显然那个孩子受过虐待。It is likely that he will ring me tonight.他今晚可能给我
9、打电话。It is doubtful whether she will be able to come.她能否来还很难说。3It seems/ happened/ turned out/ suddenly struck me/ occurred to me.that .It happened that I wasnt there that day.恰好那天我不在那里。It seems that his idea is more practical.看起来他的意见更实际一些。4It be 过去分词(如：said/ reported/ announced/ decided/ expected/ h
10、oped/ known/ believed.)that.It is hoped that the number of deer will greatly increase very soon.(People hope that the number of deer will greatly increase very soon.)人们希望鹿的数目会很快增加。It is reported that more than twenty people were killed in that bus accident.据报道在那次的公共汽车事故中有二十多人丧生。即学即练3用适当的代词填空It is kn
11、own that he is one of the best teachers in our school.It suddenly occurred to me that I knew how to solve that problem.It is strange that he should have left without telling us.单句语法填空1It is very kind of you to give(give) me a hand in time.2It is still a mystery what caused the accident.3It is necess
12、ary that one (should) master(master) the skills of operating computer.4It is known to all that the gun powder was first invented by the Chinese.5It seemed certain that he will win the prize.短文语法填空I 1.have studied(study) English for six years.It was difficult for me 2.to remember(remember) new words
13、first.I tried every means, but it no use 3.reciting (recite) them over and over again.It was very kind of you 4.to offer(offer) me some suggestions.It is necessary 5.to understand(understand) its meaning in sentences.It is no wonder 6.that your English is good.It is requested 7.that everyone should master proper methods of learning.8.It was a shame that I hadnt asked you for help earlier.I will try my best to improve my English.9.It is hoped that I will pass the TOEFL and have a chance to study abroad.Thanks for your help.I would be grateful 10.if you could give me a reply soon.